The present invention relates to optical microphones and sensors. More particularly, the present invention relates to an optical microphone for measuring distances to, and/or physical properties of, a medium, in accordance with the teachings of U.S. Pat. No. 5,771,091, which teachings are incorporated herein by reference.
The device disclosed in U.S. Pat. No. 5,771,091 is a very sensitive and compact device for measuring distances to, and/or physical properties of, a medium. At the same time, often there is a need for a smaller, more compact device that will facilitate the performance of measurements within tiny available spaces in different apparatus.
It is therefore a broad object of the present invention to provide a small, optical microphone/sensor for measurement of sound pressures in microphones, static pressures in, e.g., pressure sensors, accelerations (accelerometers), temperatures (thermometers), and different other parameters in locations where it is very problematic to accommodate any other known sensors, because of their relatively large size.
The diameter of the small optical sensor of the present invention is limited and defined by the diameter of existing light waveguides, such as optical fibers, and may be in the range of less than one millimeter, or between one and two millimeters.
It is an additional object of the present invention to provide low cost, small optical microphone/sensors.
It is another object of the present invention to provide small optical microphone/sensors that are capable of working in wide ranges of temperature up to several hundred degrees Celsius.
The present invention therefore provides a small optical microphone/sensor for measuring distances to, and/or physical properties of, a reflective surface, comprising a source of light coupled to a light waveguide for transmitting a light beam through said waveguide; said waveguide having at one of its ends a pointed face or pick form end surface with an angle determined by Snell""s Law of Refraction             sin      ⁢              xe2x80x83            ⁢              α        1                    sin      ⁢              xe2x80x83            ⁢              α        2              =            n      2              n      1      
wherein xcex11 is the angle of travel of the light beam through the waveguide media; xcex12 is the angle of travel of the light beam in a second media when exiting from the pointed face, and n1 and n2 are the light indices of the light waveguide media and the second media; the reflective surface being disposed at an optimal distance from the pointed face as determined by the angle xcex12; the waveguide having, at its outer surface, at least adjacent to the pointed face, means for preventing light waves impinging on said surface from being reflected back into the waveguide, and a light detector arranged to receive the light reflected from said surface.